1. Field of the Invention
The present invention generally relates to an assembly for mounting an electric or electronic device to a printed circuit board of an electronic system, to an electronic system incorporating the assembly, and to a method for mounting an electric or electronic device to a printed circuit board.
2. Description of the Prior Art
FIG. 1 shows a simplified diagram of a typical potentiometer 100 which is used, for example, as a volume control in a car stereo. The potentiometer 100 includes a C-shaped fixed resistor 110 which is formed on a substrate 120. A wiper contact 130 is mounted on a pivotable shaft 140 (shown in end view) extending through a center of the substrate 120. The wiper contact 130 is positioned to slide along a surface of the fixed resistor 110 as the shaft 140 is manually pivoted in clockwise and counterclockwise directions. A first end 111 of the fixed resistor 110 is connected to a reference potential V.sub.REF through a first terminal 151, a second end 112 of the fixed resistor 110 is connected to ground through a second terminal 152, and an output voltage V.sub.OUT of the wiper contact 130 is applied to a third terminal 153.
In operation, when the shaft 140 is pivoted fully counterclockwise, the wiper contact 130 is positioned adjacent the first end 111 of the fixed resistor 110, thereby causing V.sub.OUT to substantially equal V.sub.REF. Conversely, when the shaft 140 is pivoted fully clockwise, the wiper contact 130 is positioned adjacent the second end 112 of the fixed resistor 110, causing V.sub.OUT to substantially equal 0V (ground). When the shaft 140 is pivoted to position the wiper contact 130 between the first and second ends of the fixed resistor 110, the resulting circuit acts as a voltage divider such that V.sub.OUT is a portion of V.sub.REF determined by the rotated position of the shaft 140.
Potentiometers are often used as control elements in electronic systems mounted in automobiles, such as stereo volume controls and heater control units. In many applications, the potentiometers are mounted on printed circuit boards (PCBs) which are housed within an electronic system.
FIG. 2 shows a first example of a known structure for mounting potentiometers 200 onto a main PCB 210. Each potentiometer 200 includes a housing 201, which houses the fixed resistor and wiper contact (not shown), and a bushing 202 which extends from the housing 201 and surrounds a base portion of the shaft 203.
In accordance with the known structure shown in FIG. 2, the potentiometers 200 are mounted onto auxiliary PCBs 220 which are then fixedly connected to main PCB 210 using adhesive or a mounting bracket (not shown). The terminals of the potentiometers 200 are soldered to conductive traces (not shown) formed on the surfaces of the auxiliary PCBs 220, and the conductive traces are electrically connected to the pins of a connector 221. When the auxiliary PCBs 220 are mounted to main PCB 210, the bushings 202 and shafts 203 of the potentiometers 200 extend through holes 211, and the bushings are fastened to main PCB 210. Cable connectors 212 are then connected to connectors 221. As shown in FIG. 2, main PCB 210 may also include several push button switches 240 which provide additional control inputs.
A problem with the above-mentioned known structure is that it requires a substantial amount of time to mount the potentiometers onto the main PCB. In addition, if one of the potentiometers fails, it is necessary to disconnect the auxiliary PCB from the main PCB, to disconnect and replace the malfunctioning potentiometer on the auxiliary PCB, and then to reconnect the auxiliary PCB to the main PCB. This causes the overall maintenance costs of the electronic device to be very expensive.
To avoid the problems associated with the first known mounting structure (described above), a second known mounting structure includes the use of vertical mount potentiometers which are mounted and soldered directly onto the main PCB. However, vertical mount potentiometers have a disadvantage in that soldering errors can ruin the main PCB, thereby increasing overall production costs. Further, if one or more of the vertical mount potentiometers fails, it is often less expensive to replace the entire main PCB rather than remove and replace the malfunctioning potentiometer, thereby creating high maintenance costs.